Refrigeration system and method



Aug. 12, 1969 Filed March 7. 1968 H. P. PETERSON 3,460,354

REFRIGERATION SYSTEM AND METHOD 2 Sheets-Sheet 1 r 1,1? d u L- LI I II *I I! F -32 I i I I I I UH; l

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REFRIGERATION SYSTEM AND METHOD Filed March 7, 1968 2 Sheets-Sheet 2 U uu m n n u CONTROLLER Fig. 3

46 INVENTOR.

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ATTORNEYS nited States Patent Office 3,460,354 Patented Aug. 12, 19693,460,354 REFRIGERATION SYSTEM AND METHOD Hans P. Peterson, Simsbury,Conn, assignor to Dunham- Bush, Inc., West Hartford, Conn., acorporation of Delaware Filed Mar. 7, 1968, Ser. No. 711,243 Int. Cl.F25b 39/04 U.S. Cl. 62-184 8 Claims ABSTRACT OF THE DISCLOSURE There aremany refrigeration systems of the type which have the evaporatorpositioned within a building and an air-cooled condensing unitpositioned upon the roof of the building or adjacent the building. Anarrangement is disclosed for controlling the cooling effect of the airon the condenser of such a refrigeration system. The condensing unit isenclosed within a housing which has an air inlet at the bottom and anair outlet near the bottom, and the condenser is positioned near the topof the casing. Fans are provided which are operative to circulate airthrough the housing and thereby cool the condenser in a very efficientmanner. When the ambient air temperature drops sufiiciently to cause thecondenser to be cooled excessively, the fans are stopped so that thereis no longer a positive circulation of the air into and out of thehousing. The air within the housing continues to be heated by thecondenser and the housing provides an inverted pocket in which theheated air tends to accumulate. The fans also may be operated tocirculate the air through the condenser but without causing fresh air tobe circulated through the housing.

This invention relates to refrigeration systems, and more in particularto refrigeration systems of the type where the entire condensing unit ismounted outside of a building and has an air-cooled condenser which isexposed to wide variations in the temperature of the air.

An object of this invention is to provide an improved refrigerationsystem of the above character. A further object is to provide simple andefficient arrangements providing variable cooling of air-cooledcondensers. A further object is to overcome the difiiculties which arencountered with air-cooled refrigerant condensing units as a result ofexcessive cooling of the condenser. These and other objects will be inpart obvious and in part pointed out below.

Condensing units of the above type are exposed to wide variations in theoutside air temperature and there have been resultant problems anddifficulties which have interfered with eilicient and dependableoperation. When the temperature of the outside air drops, particularlynear or below the temperature of the refrigerated space, the liquidrefrigerant tends to accumulate in the condenser, and the evaporatordoes not receive liquid refrigerant in the normal manner. A great dealof effort has been expended in overcoming that condition, and manydifferent arrangements have been proposed and used. It is a furtherobject of the present invention to solve such problems. Another objectis to provide simple and efficient arrangements for controllingprecisely the amount of cooling of the refrigerant in systems of thecharacter referred to above.

In the drawings:

FIGURE 1 is a side elevation with parts broken away showing oneembodiment of the invention;

FIGURE 2 is a reduced scale representation of the condenser and fanassembly of the system of FIGURE 1; and

FIGURE 3 is a schematic representation of the electrical control systemfor the illustrative embodiment.

Referring to FIGURE 1 of the drawings, a refrigeration system 1 has acondensing unit 2 positioned upon the roof of the building andcomprising, a compressor 4, an air-cooled condenser 6, a receiver 8 andstandard auxiliaries and controls, all enclosed within a sheet metalhousing 10. The refrigeration system also has an evaporator 12 and anexpansion valve 13 which are positioned within a refrigerated space inthe building, and which are represented schematically in FIGURE 1.Housing 10 has a rigid frame construction and sheet metal walls at thetop, bottom and sides, and the housing is closed except for arectangular air inlet opening 16 in the front of the bottom wall 25, andan air outlet opening 18 beneath the front wall 20. A slanting wall 22extends between the bottom edge of opening 18 and the left-hand edge ofopening 16 and upwardly toward the center of the housing to a horizontalplate 24. Bottom wall 25 extends beneath compressor 4 to the rear wall26. Condenser 6 is a finned coil assembly of standard construction withparallel vertical faces between the side walls 29 and directly below thetop wall 28. Two fans 30 and 32 (see also FIGURE 2) are positionedside-by-side horizontally at the left of the condenser, and cowls 34close off the left-hand face of the condenser around the fans. Avertical wall 31 extends upwardly from plate 24 to the bottom of thecowls 34. Hence, housing 10 is divided by wall 22, plate 24 and wall 31to provide a vertical air inlet passageway extending upwardly fromopening 16 past the motor compressor and the other components and thencebetween the walls 31 and 26 to the rear face of the condenser. An airdischarge passageway is also provided from the left-hand face of thecondenser and the fans 30 and 32 downwardly between front Wall 20 andwall 31 to opening 18.

Fans 30 and 32 are operative to draw air from right to left through thecondenser, and that causes air to flow into the bottom of the housing,to the left through the condenser, and thence downwardly out throughopening 18. Hence, a simple air-flow path is provided which cools thecomponents of the system and the refrigerant in the condenser.

As indicated above, the present invention provides for controlledcooling of the refrigerant in condenser 6. In accomplishing thatpurpose, housing 10 provides an inverted pocket above the bottom edge 21of front wall 20 which is totally closed by the rear, side, top andfront walls. Hence, while fans 30 and 32 may be operated to pass airthrough the housing to provide maximum cooling, there is no substantialflue effect to cause a natural flow of heated air from the housing whenthe fanas arenot operating. If the fans are stopped, the air in the topof the housing, which has been heated by the condenser is lighter thanthe cold outside air surrounding the housing, and that heated airremains in the inverted pocket in the top of the housing so that thecondenser is surrounded by the heated air. Assuming that the operatingconditions are such that the circulation of the air by the fans hascaused over-cooling of the condenser, the stopping of the fans willimmediately relieve that condition.

In the illustrative embodiment there is also an arrangement forproviding a controlled amount of air cooling for the condenser.Referring to FIGURE 2, fans 30 and 32 may be operated to draw the airthrough the condenser from the rear of the housing toward the front asdiscussed above. However, the direction of fan 32 may be reversed so asto direct air from the front of the housing toward the rear through thecondenser. When operating in that the manner, the air in the top of thehousing is circulated back and forth through the condenser, but there isno positive discharge of air from housing. The air being circulated bythe fans in that manner is subjected to a limited amount of cooling byconduction through the sheet metal walls of the housing. Also, when thefans are stopped and when they are operating in opposite directions tomerely circulate air within the housing, the air in the vicinity of themotor compressor may be heated sufficiently to cause an upward flow inthe rear of the housing with a corresponding natural discharge of airthrough opening 18.

With the arrangement of the illustrative embodiment, there is a widerange in the amount of actual cooling of the refrigerant. Sequencecontroller 40 is operative to gradually reduce the cooling effect byfirst stopping motor 32, then operating motor 32 in the reversedirection, and then stopping both of the motors; and the motors may betwo-speed. In addition, the invention contemplates the use of a fanspeed controller which operates in response to the temperature orpressure of the refrigerant in the condenser to govern the power inputinto the fan motor or motors, and with a fan motor or motors whichoperate at a speed proportional to the power input. That provides anuninterrupted modulation in the air circulation. The invention alsocontemplates the possible use of a damper to close the air outletopening 18, thus to provide a positive shutting off of the airdischarge. Openings 16 and 18 may be covered with suitable screens sothat the housing is kept free from the entry of foreign materials anditems and the housing gives very adequate protection for components ofthe condensing unit.

In FIGURE 3 there is represented schematically the control system forthe operation of fans 30 and 32. Electrical current is supplied to asequence controller 40 from which lines 42 and 44 extend to bothwindings of the motor for fan 30, and line 42 also extends on one sideof the field winding 46 of the motor for fan 32. The other side of fieldwinding 46 is connected through a line 48, a switch unit 50 of a relay52 and a line 54 to line 44. The starting winding 56 of the motor forfan 32 is connected at one side through a line 58 and a switch unit 60to line 48, and the other side is connected through a line 64, a switchunit 66, and a line 68 to line 42. Hence, with relays 52 and 62positioned as shown, both of the fan motors are operated when controller40 supplies current to lines 42 and 44.

Controller 40 is also connected to the solenoids 70 and 72 of relay 52.It has been indicated above that fan 32 may be stopped while fan 30continues to operate. That is accomplished by energizing solenoid 72which raises the armature of switch unit 50 through which line 44 isconnected to the motor for fan 32, and fan 32 is stopped. Controller 40may then operate fan 32 in the reverse direction by energizing solenoid70 which closes a switch unit 74 so as to connect line 54 through a line76 to a switch unit 78. Switch unit 78 is closed by the lifting of thearmature of switch unit 50 by solenoid 72. Hence, with switch units 74and 78 closed, line 44 is connected to line 48 and thence to the fieldwinding of the motor for fan 32.

If the starting winding 56 were to remain connected as before, fan 32woulld be operated in the same direction as before. However, relay 62has a solenoid 80 which is connected at one side through line 68 to line42, and the closing of switch unit 74 connects the other side ofsolenoid through a line 88, switch unit 74 and line 54 to line 44, sothat solenoid 80 becomes energized. The ener gization of solenoid 80lifts the armatures of switch units 60 so as to reverse the connectionof lines 42 and 44 to field winding 56, so that fan 32 operates in theopposite direction. At that time, one side of winding 56 is connectedthrough line 58, switch unit 66 and line 68 to line 42, and the otherside of winding 56 is connected through line 64, switch unit 60, line48, switch unit 78, line 76, switch unit 74 and line 54 to line 44.

During operation, controller 40 acts in response to a drop in the headpressure of the compressed refrigerant passing to the condenser.Controller 4%) then carries on a sequence of steps as that head pressuredrops through a relatively narrow range. When the head pressure is abovethat range both of the condenser fans 30 and 32 operate whenever thecompressor operates. A drop in the head pressure to that range indicatesthat there is over-cooling of the condenser, and the first control stepis to stop fan 32. That reduces the amount of air circulation throughthe condenser, but fan 30 continues to operate and provides a reducedamount of cooling of the refrigerant. If the over-cooling conditioncontinues, there is a further drop in the head pressure and controller40 then starts fan 32 in the reverse direction so as to provide the aircirculation solely in the top of the housing. If the overcoolingcondition then continues, the next step of controller 40 is to stop bothfan motors by cutting off the power to lines 42 and 44. It is thus seenthat controller 40 modulates the amount of cooling which is performedupon the refrigerant in condenser 6 to maintain the proper condition.

In this embodiment, compressor 4 is driven by an electric motor which isenclosed within the same housing. The particular control arrangementillustrated in the drawing provides a very practical mode of modulatingthe cooling. The invention contemplates that other control arrangementsmay-be provided and that the apparatus and the mode of operation may bemodified.

What is claimed is:

1. In a refrigeration system, the combination of, an evaporatorpositioned to perform a cooling function by the evaporation ofrefrigerant therein, a condensing unit to supply liquid refrigerant tosaid evaporator and to withdraw and condense the evaporated refrigerant,said condensing unit including an air cooling condenser, a housingenclosing said condenser and providing an inverted air pocket for air tocool said condenser, said housing being closed from its top downwardlyto a level substantially below the bottom of said condenser and havingstructure therebelow which provides for the entry of air into saidpocket and the discharge of air therefrom, fan means to circulate airthrough said pocket in heat exchange relationship with said condenser,and control means to modulate the air flow between a condition whereinsaid fan means directs a maximum amount of air therethrough and acondition wherein there is substantially no air flow therethrough.

2. A system as described in claim 1, wherein said fan means comprises aplurality of electric fans, and said control means comprises a sequencecontroller.

3. A system as described in claim 2, wherein said condenser has verticalfaces transverse to the flow of air therethrough and wherein said fanscomprise two fans in side-by-side relationship horizontally spaced alongone of said faces, and wherein said controller operates in response tothe pressure of the condensed refrigerant.

4. A system as described in claim 3, wherein said fans operate inparallel to draw air through said condenser when the refrigerantpressure is above a predetermined value and upon successive decreases insaid refrigerant pressure, said fans are operated to successivelydecrease the air flow.

5. A system as described in claim 1, wherein said housing has a bottomwall with an air inlet opening therein and a side wall with an airoutlet opening therein, and partition means providing air passageways toand from the opposite faces of said condenser. v

6. A system described in claim 5, wherein said compressor is mounted onsaid bottom wall in the path of the air entering said inlet opening.

7. A condensing unit for a refrigeration system comprising a compressorhaving an electric motor which drives it, a receiver, a condenser,refrigerant lines providing a refrigerant flow path to and from saidcompressor, said condenser, and said receiver, a housing providing aninverted air pocket and air inlet and discharge paths for said pocket,said condenser being positioned within said pocket whereby it issurrounded by air which tends to become stratified within said pocketwhen heated above the temperature of the air surrounding said housingand control means to provide controlled air circulation to cool saidcondenser.

8. Apparatus as described in claim 7, wherein said control meanscomprises fan means and a controller responsive to a drop in thepressure-temperature condition of the refrigerant in the condenser.

References Cited UNITED STATES PATENTS 15 WILLIAM J. WYE, PrimaryExaminer US. Cl. X.R. 62507

